1. Field of the Invention
The present invention relates to the design and simulation of logic circuits.
2. Description of the Related Art
A logic circuit comprises a set of logic gates that are interconnected using wires (also referred to as "nets" or signals). Simulation of a circuit involves supplying input stimuli to the circuit at its input ports, and determining the response of the circuit at its output ports. Such simulation is normally done using a software program that models the components used in the circuit at an appropriate level, and that emulates the reaction of the circuit components to the input stimuli (i.e., the "input events") in accordance with operational semantics. The speed of a simulation depends on many factors, including the level of detail at which the circuit is modeled (e.g., semiconductor-level modeling, binary 0-1 logic levels, etc.) and the speed of the underlying execution engine.
Several patents assigned to Quicktum Design Systems, Inc., of Mountain View, Calif., disclose techniques for debugging a circuit on reconfigurable emulation systems, for example, U.S. Pat. Nos. 5,425,036 (Liu et al.), 5,448,522 (Huang), 5,448,496 (Butts et al.), 5,452,231 (Butts et al.), 5,452,239 (Dai et al.), 5,475,830 (Chen et al.), and 5,477,475 (Sample et al.), the teachings of all of which are incorporated herein by reference and referred to herein collectively as "the Quickturn technology". The Quickturn technology involves timed circuit simulation using field programmable gate arrays ("FPGAs") and techniques to map a circuit onto FPGAs without a timing problem. FPGAs are devices that provide a target technology onto which an arbitrary circuit designed for a particular application can be mapped. However, the timing of the mapped circuit, other than the storage elements, cannot be easily controlled, because the interconnection delays usually dominate the overall delay on FPGAs. The Quickturn technology relies on the physical characteristics of the FPGA, and assumes use of XILINX brand FPGAs from Xilinx Corporation. The result is that the Quickturn technology is not general, and is limited to identifying hold-time problems in 100% synchronous circuits. The Quickturn technology does not address the asynchronous portions of logic circuits which typically cause the most debugging problems.
It is an aspect of the present invention to provide an improved technique for simulating a logic circuit onto an FPGA-based platform.
Further aspects and advantages of this invention will become apparent from the detailed description which follows.